1. Field
The field of the invention is snow conditioning and grooming devices which chop, grind, and stir the snow, and more particularly such devices for producing rolling ski paths by thoroughly grooming uneven snow surfaces without excessively flattening their contours.
2. State of the Art
Various snow-grooming devices have been used to smooth and recondition snow surfaces for ski slopes, generally being drawn over the snow behind a tracked vehicle. Examples are unpowered harrows, rotating discs, rollers and the like to break up and level the snow surface. In contrast, snow tiller are powered to agressively break up and cut the snow so that the conditioned surface is relatively fine grained, and preferably lightly but firmly packed for easy, enjoyable skiing. Such tillers comprise elongate, toothed cutter bars mounted on frames and powered to rotate by vehicle power takeoffs, or separate independent combustion or hydraulic engines mounted directly on the tiller frame. See U.S. Pat. No. 4,359,831. The cutter bar teeth may be radially projecting blades or spikes. In some instances appended lengths of chain are used to mulch the snow surface.
The tillers are towed by endless track vehicles, and must groom paths of 12 to 16 feet to cover the track marks. Typically, the entire path is groomed all across by a rigid. cutter bar. The rigid cutter bar cannot conform to sinuously rolling snow surfaces, tending to work the high places but bridge over the valleys between. Rolling paths thus tend to be reduced to quite flat ones. It is difficult or impossible to produce uniformly groomed yet rolling paths, which are very enjoyable to ski and are desirably slower and safer. Some present tillers do have provisions allowing them to freely rotate about an axis in the direction of travel. U.S. Pat. No. 4,359,831, for example, incorporates an "oscillation" bar and coupling for this purpose. Such devices allow the cutters to act somewhat independently of the towing vehicle attitudes to better conform to rough snow surfaces. They fail to alleviate the bridging problem discussed above. Nor does the two segment, "flexibly coupled" cutter bar of said patent. The two axially aligned cutter bar segments are coupled only sufficiently flexible to relieve bearing alignment and frame deflection problems. The coupling flexes only to compensate for any deflection of the tiller frame, so that the cutter segments remain substantially aligned. The bridging problem is therefore not substantially relieved.
At least one attempt has been made to replace the monolithic cutter bars with bars having a pair of sections coupled by a connector capable of bending through large angles. See the "Information Disclosure" filed herewith. High flexure couplings appear to be also required at the outside ends of the cutter bar, and the constantly changing distance between these ends must somehow be accommodated. The coupled two part cutter bar can bend with respect to its mounting frame, to somewhat alleviate the bridging. However, the frame is believed to be rigid and monolithic. The attached snow apron and grooming or compactor bar, are also monolithic and therefore cannot follow the flexing cutter bar, so that any grooming advantages are largely cancelled.